The Effect of Forecasting Accuracy on the Sizing of Energy Storage

The purpose of this research is to the problem of optimal sizing of energy storage required for compensation of wind farm generation variability. Using wind farm production data from the BPA, we assess the effect of forecast quality and economic dispatch timing on the size of storage and critical power rating required to nearly perfectly match the committed energy. We develop a Model-Predictive-Control (MPC) based operational model following NERC standard recommendations. Different forecasts are considered and compared from the storage sizing perspective. The results of our simulations can be fit by two simple relations, connecting the storage sizing with forecast error, wind variability, and the timescales of scheduling. A more accurate forecast reduces the storage sizing. However, diminishing returns are observed when the forecast error becomes comparable to natural wind variability within the commitment time interval. The proposed methodology can be extended to other systems with intermittent generation and controllable real or virtual storage.